Heavy goods vehicles (HGVs) are synonymous with high fuel consumption due to their weight and bluff nature. At a time when fuel prices are high and haulage operators have an environmental responsibility to reduce CO2 emissions, there is great interest in the possible methods of curbing fuel consumption. With up to 50 percent of HGV fuel consumption attributed to aerodynamic drag, there are improvements which can be made to the design and manufacture of haulage trailers in order to reduce fuel consumption and reduce CO2 emissions. Various design modifications, both those able to be retrofitted and only possible at the point of manufacture, are tested using computational fluid dynamics (CFD), to establish the potential drag reduction when compared to a baseline case. These are evaluated in both normal and side-wind conditions. The baseline case is modelled to represent a HGV combination that is representative of the average trailer in operation in the UK industry. It is found that in combination, the trailer modifications analysed can reduce the aerodynamic drag of the overall vehicle geometry by up to 26%. Additional geometry is also tested that is specific to the UK industry due to the lack of a limitation on overall vehicle height. These tests highlight the consequences of unchecked vehicle geometry and the effects that inappropriate truck and trailer matching can have on the overall drag contribution of the vehicle. These cases along with the comparative and baseline cases show that the ow characteristics of the vehicle geometry differs greatly between normal and conditions of side-wind. This in turn dictates the e effctiveness of the geometry modifications dependent on their intended area of drag improvement, and can inform design decisions when incorporating these at the point of manufacture.